Trailer math

[bdog]

I have a tandem axle gooseneck trailer with a fixed load on it. It has two 7k axles.

From the hitch to the center of the tandems is 22'. I want to move the axles forward to reduce the tongue weight. Right now it weighs 10,520 on the axles and 2,240 on the tongue. I know that really isn't out of line percentage wise for a gooseneck but it is too much weight on our 3/4 ton. It will pull it fine I know but we need to be legal for DOT scales and such as this is a commercial vehicle. I am within my max gross combined tow rating but the GVWR on my truck is 10,000 and with the trailer hitched I am within 300lbs of the max with just the driver. We often take 4 people in this truck plus their luggage in the bed.

So I have :

12,760 gross
10,520 on axles
2,240 on tongue
Axle center 22' from hitch

I want it to be around 1,500 on the tongue, and 11,260 on the axles. How far forward do I need to move the trailer axles?

 

[RedNeckRacin]

I think you need to rethink this. Tongue weight isn't a hinderance, it helps with pulling and braking. Get a bigger truck.

 

[bdog]

The trailer has good brakes. It isn't really close to being overloaded in terms of gross weight it is just the way the load sets on the trailer that makes the tongue heavy. The load can't be moved either it is welded in place on the trailer.

I don't think transferring 740lbs from the truck to the trailer in a 20,000lb rig is going to make it unsafe.

Buying another truck is not an option.

 

[kebo]

The trailer has good brakes. It isn't really close to being overloaded in terms of gross weight it is just the way the load sets on the trailer that makes the tongue heavy. The load can't be moved either it is welded in place on the trailer.

I don't think transferring 740lbs from the truck to the trailer in a 20,000lb rig is going to make it unsafe.

Buying another truck is not an option.

Would be curious to learn what kind of load you carry that is welded to the trailer??

As for relocating both axles more forward, I can't really offer any advice, but.... your assertion that moving them forward to adjust the tongue weight should not make the whole rig unsafe is probably correct. However, you won't know that for certain unless you try it and see.

However, I just wonder if the DOT people could ever know if the trailer had been modified from its original design, and if they knew it was modified, would they do anything about it?? Don't trailers have to be certified for highway use, once they get above a certain rating?? If yes, then would modifying it make the certification void? I have no experience above a 16ft trailer, so just asking some questions to learn something.

 

[bdog]

The trailer has some specialty oilfield equipment on it.

I don't think it will be a problem legally moving them. I have built trailers from scratch before with no problems. It just has to pass the safety inspection each year.

 

[dieselcrawler]

I'm sure there are complex math equations to figure it out, but I'm sure more information would be needed.

Myself, I would cut the axles loose, make a sub-frame, if only temporary, to hold the axle mounts in their proper places, slide them up until late you get the change in ballance you want then reattach. Crude, but would work.

 

[4570Man]

I'm thinking it might be easier to unweld the equipment and move it back a few inches instead of moving the axels.

 

[JCByrd24]

I'm in bed on my phone but will do the math/statics problem for you tomorrow. It's too cold here in Maine to do anything else!! I see no issue with your solution.

 

[Green Power]

I'm thinking it might be easier to unweld the equipment and move it back a few inches instead of moving the axels.

He needs all the deck space he can get. http://www.tractorbynet.com/forums/...9019-mounting-trailer-trailer.html?highlight=

 

[Ron50]

As is you are at 17.555% of load transfered to the tongue which is 2,240#. If you want 1500# transfered to tongue weight you need11.755% of load on tougue. Axels are 3.8621 feet behind center of load. You need them at 2.5861 behind center of load. You need to move axels forward 1.276 feet.
Best I can do, someone else could confirm or not.